Biomechanical sole unit

ABSTRACT

A shoe sole unit having a polymeric tread including a plurality of lateral structures extending along the midportion of the sole unit and seated in the interior of the tread. The shoe sole unit also has two longitudinal structures to link the lateral structures as well as a heel cradle.

BACKGROUND OF THE INVENTION

[0001] The invention relates to sole units, specifically to biomechanical analogous components molded into either the outsole or midsole to increase lateral stiffness while returning energy from the natural flexion movements of the foot during walking or running activities.

[0002] In recent years there has been an upsurge of technological advances in the footwear industry. The advances have been to make footwear more comfortable while including anatomically beneficial results, i.e. to reduce injuries. Some ideas have improved the outsole whereas other inventions have been focused on the midsole, the material which generally lies above the outsole.

[0003] FIGS. 9-12 have been included to assist in the descriptions of a human foot as they illustrate the bones and other skeletal and ligament features.

[0004] U.S. Pat. No. 5,625,964 discloses a design for a recreational, occupational or casual footwear with a symmetrical heel cradle that addresses the rear foot strike zone. The design elements provide differential cushioning and shock attenuation during the rear foot heel strike moment. In doing so, it also achieves a medial and lateral stability of the calcaneus (heel bone) aiding in the support of the foot structure during the weight acceptance and shifting transitions of normal gait. Lateral and medial longitudinal segments are articulated in relation to each other through the midsole portion, whereby the heel support member does not significantly impede articulation of the rear foot strike zone about the line of potential flexion. The two chambers extend into the forefoot area of the sole with a tapering along its extending length to the end of the forefoot. Further description of the unit displays a plurality of adjacent passageways extending transversely from the broader chambers connecting with the exterior solid side passageways. The passageways serve as re-enforcing members and complete a third and fourth chamber while in fluid communication with each other.

[0005] U.S. Pat. No. 5,806,209 discloses a shoe cushioning system having a thin midsole, a medial forefoot element, a lateral forefoot element and a heel element. The heel element includes an elastically deformable cushion and a cap. As the heel element strikes a surface during running, the heel cushion operates to absorb the impact forces from the runners' foot while also providing a stable platform for the runner when the foot first makes contact with the ground.

[0006] Disclosed in U.S. Pat. No. 5,794,359 is shoe sole and heel structure which have fluid cavities at the peripheral edges of the ground-contacting surface of the structure to provide both lateral stability and cushioning. Described are two sets of four channel cavities molded into the outsole. Each channel cavity opens at the interior surface and extends between and opens into two associated adjacent lateral cavities to fluidly connect all five lateral cavities together in order to maintain the integrity of the biomechanical sole unit.

[0007] There have been some difficulties with these types of soles. If any of the chambers is punctured, the air escapes and thus there is no fluid flow to accommodate the cushioning effects of the sole.

[0008] U.S. Pat. No. 5,987,782 is directed to a high-traction sole unit which includes a series of more or less rigid lattice inserts or lamina. Each of them is composed of a series of transverse inverted T ribs having their axis perpendicular to an S-Shaped dorsal line ideally representing the rolling axis.

[0009] The natural motion of walking includes a heel strike followed by a forward motion of the tibia and fibula of the lower leg. This forward motion is met with resistance forcing a downward force in the tarsal and metatarsal bones of the foot resulting in a stretch on the plantar ligament.

[0010] The stretch on the plantar ligament, which has an approximate 3% compliance, cause the ligament to be pulled much like a rubber band (See FIG. 12). This maximum stretch of tissue represents potential energy stored in the structure and tissues of the foot. At the point that the ball of the foot, approximately 55 to 60 degrees of forefoot bending, being to unload the weight of the leg and thus releases that stored potential energy providing the muscles with temporary assistance in lifting the foot. This action is commonly referred to as passive tension in the muscle but adds to the total potential tension development of muscle force.

[0011] The biomechanical matrix replicates this principle by extension of the materials and the structural interaction with the outsole and midsole components of footwear. The unit provides an important skeletal support to the outsole for the medial and lateral forces experienced by the foot-ground interaction while responding exactly like tissues when stretched during forefoot flexion. At that point, the biomechanical matrix stretches, becoming more rigid as it stores potential energy, again much like a pulled rubber band. As the leg begins to unload and shift its weight to the other leg, the leg becomes lighter and permits the release of that stored energy in the matrix thereby assisting the muscles in push off. This muscle assistance results in reduced muscle activity and reducing the onset of muscle fatigue.

SUMMARY OF THE INVENTION

[0012] An object of the present invention is to provide a sole design that has an increased lateral stiffness while maintaining longitudinal flexibility.

[0013] Another object of the invention is to provide an energy return configuration that enhances the natural forward progression of the foot structure and in doing so will reduce the onset of muscle fatigue.

[0014] A further object is to provide a shoe having good sensitivity and stability on the ground followed by good adsorption of impact force during the step.

[0015] Another object is to provide a rounded opening at the heel area to impart a greater shock attenuation and afford improved heel control when accepting body weight during heel strike.

[0016] Still another objective is to provide superior lateral stability and curtail the onset of muscle fatigue which will assist in reducing injuries to the ankle and lower extremity particularly for recreational footwear activities.

[0017] Briefly, according to the present invention, a shoe sole unit which includes a polymeric tread, a plurality of lateral structures extending along the mid-portion of the sole unit and at least one longitudinal structure to link the lateral structures. Typically, there is a pair of longitudinal structures linking the lateral structures, one longer structure on the medial side and one shorter structure on the lateral side of the sole unit. There is a circular structure at the heel area of the unit that is an extension of the longitudinal structures. The circular sweep of the longitudinal structures at the heel includes a symmetrical heel cradle to permit cushioning for shock attenuation and to permit the heel to seat in the space during heel strike thus providing side-to-side control during the initial weight acceptance phase.

[0018] These and other objects, features and advantages of the present invention will become apparent in light of the following detailed description of preferred embodiments thereof, as illustrated in the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0019]FIG. 1 is a side view of a foot at rest;

[0020]FIG. 2 is a rear view of the foot of FIG. 1 at rest;

[0021]FIG. 3 is a side view of a foot as it strikes a surface;

[0022]FIG. 4 is a rear view of the foot of FIG. 3

[0023]FIG. 5 is a side view of a typical shoe sole;

[0024]FIG. 6 is a top view of a structure of an insert which is placed in a sole unit;

[0025]FIG. 7 is a perspective view of the insert;

[0026]FIG. 8 is an enlarged perspective view of the rear portion of the insert.

[0027]FIG. 9 is a top plan view of a foot;

[0028]FIG. 10 is a top plan view of a foot;

[0029]FIG. 11 is a sectional side elevational view of a foot; and

[0030]FIG. 12 is a sectional side elevational view of a foot.

DETAILED DESCRIPTION OF THE INVENTION

[0031] Initially with reference to FIGS. 1-4, a right foot 10 is shown. FIGS. 1 and 2 illustrate a foot at rest. While FIGS. 3 and 4 demonstrate the stress on the foot 10 as it strikes a surface. As shown in FIGS. 3 and 4 there is strain placed on many of the ligaments and tendons in the foot and the heel may evert. The stress placed in the foot will vary depending on the person's age, weight, height, sex, shoe size, stride length, and step length.

[0032] The natural motion of walking involves a heel strike followed by a forward motion of the tibia and fibula of the lower leg. This forward motion is met with resistance forcing a downward force on the tarsal and metatarsal bones of the foot resulting in a stretch on the plantar ligament. The stretch on the plantar ligament, which has an approximate 3% compliance, causes the ligament to be pulled much like a rubber band. This maximum stretch of tissue represents potential energy stored in the structure and tissues of the foot. At the point that the ball of the foot, approximately 55-60 degrees of forefoot bending, begins to unload the weight of the leg and thus releases the stored potential energy providing the muscles with temporary assistance in lifting the foot. This action is commonly referred to as passive tension in the muscle but adds to the total potential tension development of muscle force.

[0033] With reference to FIG. 5, a shoe sole unit is indicated at 14. The shoe sole unit includes the bottom portion including tread, a heel, a midportion and a forefront. The sole unit is typically manufactured from a polymeric material such as vulcanized rubber. The bottom of the shoe sole unit includes the tread. The tread may be of any design and is usually different depending on the type of shoe being produced. For example, a different design tread would be used on the bottom of a sneaker, hiking boot, walking shoe, etc.

[0034] A plurality of structures 16 are positioned within the sole unit as close as possible to the ground, to reduce to a minimum the elastic element interposed between the part connected to the lattice and the sole bearing surface. Preferably the structures are constructed of a rigid material engineered strictly for this use. There is a series of transverse, substantially oval inserts 18 having their axis perpendicular to an S-shaped dorsal line ideally representing the rolling axis. The lateral inserts are relatively thin in the range of about 1 to 3 mm thick, about 5 to 12 mm wide and about 50 to 110 mm long. They are positioned about 5 to 15 mm apart from one another.

[0035] To provide energy return, lengthwise structures or inserts 20 a, 20 b link the lateral structures 18. As shown in FIG. 6, the lengthwise structures 20 a, 20 b are positioned along the outer edges of the lateral structures 18 and are substantially parallel to the imaginary longitudinal axis of the shoe sole. Typically, there is a pair of longitudinal structures linking the lateral structures, one longer structure 20 a on the medial side and one shorter structure 20 b on the lateral side of the sole unit. The figure illustrates two lengthwise structures, however the particular shoe design may vary, for instance there may be only one lengthwise structure or the design may include three or four, etc. The lengthwise structures 20 a, 20 b are about one half the thickness of the lateral inserts 18, i.e. about 0.5 to 3 mm thick. The lateral and longitudinal structures generally are linked together during a molding process.

[0036] As shown in FIGS. 6-8, the lateral inserts include extensions 22 from the lateral inserts 18 to two additional longitudinal inserts 24. These add structural support to the design and maintain integrity during co-molding processes. The extensions are optional and are not required for the insert to have the desired effect. This will depend upon the chosen construction method.

[0037] A symmetrical heel cradle may be included in the heel of the sole unit as indicated at 26.

[0038] The heel cradle includes two semi-circular segments 28, 30. The heel cradle has approximately the same thickness of the lateral and lengthwise structures. The heel cradle will attenuate the landing shock at the heel by cradling the calcaneus bone during a heel strike. The last lateral element 32 is connected to the heel cradle during the molding process or can be left as a separate unit to aid in stock attention when used in certain constructions.

[0039] The inserts and heel cradle are depicted as generally flat pieces with rounded edges, however, the general cross-section may be altered without losing the beneficial aspects of the inserts. Depending on their exact shapes and their thickness, the combination of material increase or decrease the supporting effect on the sole unit. The flat pieces may also be cupped for added rigidity. The nature and type of materials are therefore directly related to the final characteristics required by the user and will also depend on the torsional rigidity, the lateral flexing moment, longitudinal flexibility, and the weight.

[0040] The inserts may be formed of different materials such as carbon fiber, polymeric material such as nylons, ethylene vinyl acetate (EVA), thermal plastic urethane (TPU), polypropylene, fiber-filled thermoplastic material or other similar engineered materials. The selection of the materials will be based upon the final characteristics required by the user, depending on the potential use by the wearer of the shoe sole, i.e. for mountain climbing, running, walking, playing soccer, etc.

[0041] In one specific embodiment, the outsole is 30 mm thick and has a length of 330 mm. The length of the insert is 285 mm long, 170 mm wide and has a thickness of 2 mm. The heel cradle in approximately 65 mm in diameter and is attached to the lengthwise structures during the molding process.

[0042] The lateral and longitudinal inserts along with the heel cradle, may be molded before or during the molding of the sole unit depending on the materials selected.

[0043] The combination of superior lateral support and energy return at the particular phase of human gait will provide for improved weight transfer from one leg to the other. This improvement will also result in more efficient use of muscle force and further reduce the onset of muscle fatigue as observed in lower leg electromyography or electrical muscle activity. The consequence of this unit would be a more stable transfer of weight from one leg to the other and is paramount for normal and safe walking, running or a range of recreational and occupational needs.

[0044] The foregoing description has been limited to a specific embodiment of the invention. It will be apparent, however, that variations and modifications can be made to the invention, with the attainment of some or all of the advantages. Therefore, it is the object of the claims to cover all such variations and modifications as come within the true spirit and scope of the invention. 

What is claimed is:
 1. A shoe sole unit comprising: a polymeric tread; a plurality of lateral structures extending along the midportion of the sole unit and seated in an interior of said tread; at least one longitudinal structure to link the lateral structures.
 2. The shoe sole unit of claim one wherein there are two longitudinal structures.
 3. The sole unit of claim 1, further comprising a heel cradle.
 4. The sole unit of claim 3, wherein said heel cradle is symmetrical.
 5. The sole unit of claim 1, wherein the lateral structures and the at least one longitudinal structures are selected from the group consisting essentially of carbon fiber, polymeric material such as nylons, ethylene vinyl acetate (EVA), thermal plastic urethane (TPU), fiber-filled thermoplastic material
 6. The sole unit of claim 1, wherein the lateral elements are separated by approximately 12 mm
 7. The sole unit of claim 1, wherein the lateral and longitudinal elements are connected during the molding process.
 8. The sole unit of claim 1, wherein the inserts are about 1 to about 3 mm thick.
 9. The lateral sole unit of claim 1, wherein the lateral inserts are about 5 to about 12 mm/inches wide.
 10. A shoe sole unit comprising: a polymeric tread; a plurality of lateral structures extending along the midportion of the sole unit; at least one longitudinal structure to link the lateral structures; and a heel cradle.
 11. The shoe sole unit of claim 10, wherein the sole unit includes two longitudinal structures. 